The invention relates to an internal combustion engine with cylinders including pistons movably disposed therein via a crankshaft and piston rods and an arrangement for changing the compression ratio of the cylinders and also a method for operating an internal combustion engine with a variable compression ratio.
EP 1 307 642 B1 discloses a reciprocating-piston internal combustion engine having a device for varying the compression ratio. The device has, for one cylinder of the internal combustion engine, a main piston rod which is connected to a piston, a transverse lever which is connected by means of revolute joints to the main piston rod and to the crankshaft, an auxiliary piston rod which is connected by means of revolute joints to the transverse lever and to an eccentric, and a drive device for an adjusting shaft on which is arranged an eccentric which is assigned to the at least one cylinder.
By means of rotation of the adjusting shaft and therefore by means of rotation of the eccentric, the position and the setting of the auxiliary piston rod and of the transverse lever is varied, whereby for a constant position of the crankshaft, the main piston rod is moved. The position of the piston of the internal combustion engine is therefore moved, and the compression ratio is varied. The adjusting shaft with the eccentric performs a rotational movement which is synchronous with the crankshaft, or it is rotated by means of an adjusting device (not shown). The device is suitable for adjusting the compression ratio while simultaneously improving the running smoothness of the engine.
DE 30 04 402 A1 discloses a device for adjusting the compression ratio of reciprocating-piston internal combustion engines in which the center of the crankshaft can be adjusted relative to the position of the cylinder by means of an eccentric bearing arrangement, whereby the compression ratio is varied.
EP 0 640 176 B1 likewise discloses a device for adjusting the compression ratio of reciprocating piston internal combustion engines, in which the cylinders are tilted relative to the housing of the internal combustion engine by means of an eccentric, which is mounted on an adjusting shaft, and levers. In this way, the position of the upper edge of the cylinder relative to the center of the crankshaft is varied, and, as a result, the compression ratio is changed during the adjusting process.
DE 102 21 334 A1 likewise discloses a device for adjusting the compression ratio of reciprocating-piston internal combustion engines, in which, similarly to EP 0 640 176 B1, the upper edge of the cylinder is moved relative to the center of the crankshaft. In this case, the upper part of the cylinder housing is moved in a translatory fashion by means of two eccentrics which are mounted on adjusting shafts, and the compression ratio is thereby varied.
DE 100 26 634 A1 likewise discloses a device for adjusting the compression ratio of reciprocating-piston internal combustion engines, in which an eccentric is arranged between the piston rod and the piston of the internal combustion engine. Said eccentric can be adjusted externally by an adjusting shaft via levers, whereby the compression ratio is likewise varied.
A feature of all of said reciprocating-piston internal combustion engines is the variation of the compression ratio by means of the rotation of at least one adjusting shaft.
It is the principal object of the present invention to provide, a compression ratio adjusting device which is operable at all times in a simple manner and with little energy input.